Plasma Technology for Phosphogypsum Treatment

The phosphate industry generates a large amount of waste called phosphogypsum (PG). Generally, this waste is discharged without any treatment, and it causes considerable environmental problems. Hence, the objective of this study is the treatment of phosphate waste using thermal plasma technology. First, the waste is characterized using different techniques, such as X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and inductively coupled plasma (ICP). Such characterization shows that the waste contains different toxic elements, such as heavy metals, fluorine, chlorine, sulfur, and phosphorus. For this reason, a plasma reactor is used to separate toxic elements from metals, such as silicon, aluminum, and magnesium, with a pyrolysis/combustion plasma system. In this work, the influence of different parameters, such as time of treatment and plasma current, on the volatility of toxic elements is studied. The obtained results show that after 40 min of treatment and at a plasma current of 160 A, the phosphogypsum completely melts, and the most toxic elements, namely Pb, Cd, V, Cr, and As, are completely vaporized

GC-MS analysis and antibacterial activities of some plants belonging to the genus Euphorbia on selected bacterial isolates

Plant extracts have always been used as an alternative source of antimicrobial compounds. The recent spread of multi-drug-resistant bacteria and their increased treatment costs necessitated the study of alternative, cheap sources. The family Euphorbiaceae has over 300 genera and is widely used in traditional medicine. Euphorbia triaculeata, E. fractiflexa, and E. inarticulata were selected to study the antibacterial activity of the methanolic extract against 13 Gram-positive Staphylococcus aureus strains (including methicillin-resistant S. aureus) and 2 Gram-negative isolates, Escherichia coli and Klebsiella pneumoniae, by the Kirby Bauer Disc diffusion test. Paper discs with different concentrations of the extracts (100, 50, and 25 µg mL−1) were prepared, along with the methanol control and standard antibiotic control. A gas chromatography-mass spectrometry (GC/MS) analysis was done to study the phytochemical components present in the plant methanolic extracts. A total of 50 different phytochemical compounds with antibacterial activity were detected by GC/MS analysis of the plants. Twenty-five compounds were detected in E. inarticulata, 24 in E. triaculeata, and 21 in E. fractiflexa. Out of 37 compounds found in E. inarticulata and E. triaculeata, 12 (32.43%) were common to both. Eleven (22%) compounds were unique to E. inarticulata, while 9 (18%) compounds were unique to E. triaculeata, and 13 (26%) compounds were unique to E. fractiflexa. E. fractiflexa showed the best antibacterial activity against MRSA and Gram-negative bacteria. It also showed higher unique compounds with antibacterial activity (26%), followed by E. inarticulata (11, 22%). This is the first GC/MS analysis and antimicrobial activity report of E. triaculeata and E. fractiflexa

A Developed Plasmatron Design to Enhance Production of Hydrogen in Synthesis Gas Produced by a Fuel Reformer System

Feeding IC engines with hydrogen-rich syngas as an admixture to hydrocarbon fuels can decrease pollutant emissions, particularly NOx. It offers a potential technique for low-environmental impact hydrocarbon fuel use in automotive applications. However, hydrogen-rich reformate gas (syngas) production via fuel reforming still needs more research and optimization. In this paper, we describe the effect of a plasma torch assembly design on syngas yield and composition during plasma-assisted reforming of gasoline. Additionally, erosion resistance of the cathode-emitting material under the conditions of gasoline reforming was studied, using hafnium metal and lanthanated tungsten alloy. The gasoline reforming was performed with a noncatalytic, nonthermal, low-current plasma system in the conditions of partial oxidation in an air and steam mixture. To find the most efficient plasma torch assembly configuration in terms of hydrogen production yield, four types of anode design were tested, i.e., two types of the swirl ring, and two cathode materials while varying the inlet air and fuel flow rates. The experimental results showed that hydrogen was the highest proportion of the produced syngas. The smooth funnel shape anode design in Ring 1 at air/fuel flow rates of 24/4, 27/4.5, and 30/5 g/min, respectively, was more effective than the edged funnel shape. Lanthanated tungsten alloy displayed higher erosion resistance than hafnium metal

Test-based De-isolation in COVID-19 Immunocompromised patients: Ct value versus SARS-CoV-2 viral cultures

Background Immunocompromised patients with coronavirus disease 2019 (COVID-19) have prolonged infectious viral shedding for more than 20 days. A test-based approach is suggested for de-isolation of these patients. Methods The strategy was evaluated by comparing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load (cycle threshold (Ct) values) and viral culture at the time of hospital discharge in a series of 13 COVID-19 patients: six immunocompetent and seven immunocompromised (five solid organ transplant patients, one lymphoma patient, and one hepatocellular carcinoma patient). Results Three of the 13 (23%) patients had positive viral cultures: one patient with lymphoma (on day 16) and two immunocompetent patients (on day 7 and day 11). Eighty percent of the patients had negative viral cultures and had a mean Ct value of 20.5. None of the solid organ transplant recipients had positive viral cultures. Conclusions The mean Ct value for negative viral cultures was 20.5 in this case series of immunocompromised patients. Unlike those with hematological malignancies, none of the solid organ transplant patients had positive viral cultures. Adopting the test-based approach for all immunocompromised patients may lead to prolonged quarantine. Large-scale studies in disease-specific populations are needed to determine whether a test-based approach versus a symptom-based approach or a combination is applicable for the de-isolation of various immunocompromised patients